Spring for use in limiting torque in valve operators



United States Patent [72] Inventor Daniel R. McNeal, Jr.

Gwynedd, Pennsylvania [21] Appl. No. 797,559 1 [22] Filed Feb. 7, 1969[45] Patented Nov. 3, 1970 {73] Assignee Andale Company Lansdale,Pennsylvania a corporation of Pennsylvania [54] SPRING FOR USE INLIMITING TORQUE IN VALVE OPERATORS 3 Claims, 3 Drawing Figs. [52] US.Cl. 192/150; 74/801; 251/134 [51] Int. Cl. F16p 7/02; F16h 1/28; Flk31/05 [50] Field ofSearch 251/134, 26; 74/801; 192/150; 74/626 [56]References Cited UNITED STATES PATENTS 1,883,164 10/1932 Vassakos192/150 Kuhn.....

Primary Examiner- Arthur T. McKeon Attorney-Synnestvedt and LechnerABSTRACT: Valve equipment including a rotative valve operating mechanismand power means for driving the rotative operating mechanism includinga'motor and gearing interconnecting the motor and the operatingmechanism, the gearing incorporating a gear element serving as areaction point during the transmission of torque through the gearing andmounted with freedom ,for limited movement under the influence of suchtorque transmission, together with a spring for restraining the gearelement as against such movement, the spring comprising a tapered rodmounted in cantilever from its large end and having its small end inengagement with the movable gear element.

Patented Nov; 3, 1970 Q OQAM ATTORNEY 2s Lg SPRING FOR USE IN LIMITINGTORQUE IN VALVE OPERATORS This invention relates to valve equipment andis particularly concerned with valve equipment in which the valve isadapted to be power operated through rotative mechanism. Valves of thistype commonly comprise a valve member which is movable in eitherdirection through a control range, usually by reciprocating motionbetween predetermined limits.

The power mechanism commonly includes a motor and gearing. As willreadily be understood, it is important in a system of this kind toensure shutoff of the motor, and thus to prevent abnormal rise intorque, at the end of each valve operating stroke, in order to preventdamage either to parts of the valve itself or to parts of the operatingmechanism.

For the above general purpose it has been known, forinstance in Thomaset al. US. Pat. No. 2,815,922, to provide a gearing system in the poweroperating mechanism including a gear element or member which serves as areaction point for transmission of torque through the gearing, whichelement is mounted with freedom forflimited movement under the influenceof such torque transmission, the construction further including a springfor yieldingly restraining the motion under the influence of such torquetransmission. One or more limit switches are associated with the movableelement of the gearing, these switches being operated within the rangeof motion permitted by the spring in order to shut off the motor andthus avoid excessive increase in torque at the ends of the valve stroke.

The present invention is primarily concerned with in improved form ofspring for use in an arrangement of the kind above referred to.- Havingin mind that in many power operated valve installations the valves areoperated frequently and the springs are therefore frequently flexed, theinvention provides a form of spring in which breakage from fatigue ofthe spring is diminished to such an extent that the spring replacementheretofore required is virtually eliminated.

. Another object of the present invention is the provision of a springfor the purposes referred to having identical flexing characteristics inopposite directions, so that in a reversibly operable valve operatingmechanism the spring action will be the same with respect to eithersense of rotation of the operating gearing.

How the foregoing and other objects and advantages are attained togetherwith others which will occur to those skilled in the art will appearmore fully from the following description referring to the accompanyingdrawing illustrating a preferred embodiment of the invention, and inwhich:

FIG. 1 is a vertical or axial sectional view through certain portions ofa valve operating mechanism including the threaded valve stem of thekind used with a reciprocable valve;

FIG. 2 is a vertical sectional view taken generally as indicated by thesection line 2-2 on FIG. 1, this view showing certain of the parts,including the motor, in elevation; and

FIG. 3 is a fragmentary horizontal sectional view through certainportions of the mechanism, taken as indicated by the section line 33 ofFIG-l, this view also diagrammatically indicating a motor limit switchassociated with the movable gear element.

Although the improved torque limiting spring arrangement of the presentinvention is usable with a wide variety of valve constructions, forpurposes of illustration, it is herein illustrated in association withthe general type of power operating mechanism for a valve of the kindshown in the Thomas et al. patent above identified, i.e., an arrangementin which a threaded valve stem or rod 4 extends from the valve itselffor cooperation with the rotative internally threaded sleeve or nut 5having an operating handwheel 6 keyed thereto.

In this type of construction, as is more fully disclosed in the Thomaset al. patent referred to, the power mechanism is arranged to beconnected with the handwheel, so as to effect powered actuation of thevalve by rotating the handwheel. Various details of the construction ofthe parts for effecting power rotation of the handwheel and thus poweredoperation of the valve need not be considered herein as they form nopart of the present invention per se. However, it is to be noted thatthe general arrangement comprises a driven ring gear 7 which isconnected through mechanisms generally indicated at 8 with the handwheelin order to rotate the handwheel when the ring gear 7 is power driven.

The ring gear meshes with a pinion 9 mounted on a shaft 10 the lower endof which is enlarged to provide a planetary gear carrier or spider 11.Planet gears l2 are mounted on the spider II by the shafts 13.

A central or sun gear 14 of this planetary system is mounted upon ashaft 15 carrying a bevel gear 16 meshing with the pinion 17 which isfixed on the shaft 18 of the driving motor 19. Motor 19 is preferably areversible motor in order to provide f0 operation of the valve operatingmechanism in either dirccti m.

The gearing system further includes ring gear 20 having a hub sleeve 21journaled by bearings 22 upon the shaft 15, so that the gearingcomprises an epicyclic system which is operative to transmit torque fromthe motor 19 through the gearing to the ring gear 7 connected with thehandwheel, provided the ring gt ar 20 is restrained as against rotation.The gearing element or member 20 thus serves as a reaction point for thetransmission of torque through the gearing when the valve is operated.

For the purpose of preventing extensive turning of the ring gear 20during the transmission of power, a friction band 23 surrounds the hub21, this band being split and being provided with an adjustment screw 24with a compression spring 25 arranged so as to yieldingly tighten thefriction band 23 against the hub sleeve 21. The band 23 has a lug 26 atone side which is connected with the block 27 by means of a link 28 andpivots 29. Block 27 is provided with an aperture receiving thecylindrical end portion 30a of the torque limiting spring whichcomprises a tapered rod 30 having a cylindrical portion 30b at its otherend. The cylindrical end portion 30a is at the smaller end of thetapered spring rod and the cylindrical portion 30b at the larger endthereof. The latter cylindrical portion is received and mounted in asocket 31 rigidly fastened in a portion ofthc casing for the equipment,so that the tapered spring 30 is mounted or supported from its largerend in cantilever. The spring thus tends to yieldingly restrain turningmovement of the split band 23 which in turn, because of its frictionalengagement with the hub sleeve 21. similarly yieldingly rcstrainsturning motion of the ring gear 20. The ring gear 20 thus serves as thereaction point for the transmission of torque through the gearing systemand. upon substantial increase of torque in either direction, the ringgear will move to a limited extent and in doing so will deflect the freeend of the cantilever spring in one direction or the other, dependingupon the direction of rotation of the gearing.

The foregoing action is desirable in the operation of the power meansbecause it provides a cushion to absorb shocks upon starting of themotor. In addition the arrangement is advantageously used in connectionwith limit switches for the motor. For this purpose, a plunger 32 ismounted for axial sliding movement with one end positioned adjacent tothe block 27 in which the free end 30a of the spring rod 30 is received,and the plunger 32 is desirably yieldingly urged toward the block 27, asby means of a spring (not shown). The plunger 32 carries a camdiagrammatically indicated at 33 adapted to cooperate with a camfollower 34 serving as an actuating element for the switch 35 which isadapted to be coupled into the power circuit for the motor 19 in orderto open or close the power circuit, according to the position of the cam33. Upon reaching the limit of the stroke of the valve, the rise intorque will result in deflection of the spring rod 30 and this in turnwill shift the control rod 32, thereby actuating the switch 35 to openthe motor circuit and thus stop the motor. The elements 33, 34 and 35may serve for motor shutoff in one direction of operation of the motor,and similar parts may be associated with rod 32 in positions providingfor shutoff of the motor when operating in the opposite direction ofrotation. In this latter event it will be understood that the deflectionof the spring rod 30 will take place in the opposite direction.

In order to limit the deflection of the spring 30 and thus the motion ofthe friction band 23 and associated parts, a stop element 36 is providedat the free end of the spring rod 30 in position to abut one or theother of the limiting stops 37-37 provided in the adjacent portion ofthe casing or frame structure.

The provision of the friction band 23 surrounding the hub 21 of the gearprovides an overload safety or limiting device, so that the ring gear 20may rotate with respect to the friction band in the event that thetorque or load exceeds the value represented by the deflection of thespring which would bring the stop element 36 into contact with eitherone of the abutments 37. In this way in the event of failure of thelimiting switches, damage to various parts will be avoided.

The spring arrangement of the present invention is highly advantageousin a system for limiting the operation of a power drive mechanism for avalve, for several reasons. In the first place, the employment of atapered rod as the spring element, with the rod mounted or fixed at itslarge end in cantilever results in a distribution of the deflectionloads or bending moments throughout the length of the spring element,instead of being concentrated at the fixed end. Therefore, the fatiguelife of the spring is almost infinite and the spring will not weaken orbreak adjacent the mounting as a result of fatigue. This is of especialimportance in many valve arrangements employing operating means becauseof the frequency of operation thereof.

The tapered spring rod is also desirable because the springcharacteristics are uniform with respect to deflection in two oppositedirections and, indeed, with respect to deflection in two oppositedirections in any radial plane containing the axis of the spring. Thereis therefore no necessity for positioning the spring about its axis inany particular position because it will manifest uniform bidirectionalcharacteristics in any position in which it is installed. Moreover,because of the symmetry of the spring about its longitudinal axis, thespring will not tend to take a set in one direction as compared withanother. Therefore, even where the spring is utilized to restrain thegear element constituting the reaction point for the torque transmissionthrough the gearing in both directions, there will be no tendency, overa period of use, for the action to become irregular or nonsymmetrical inone direction as compared with the other.

Still further the spring rod of the invention is highly desirablebecause of its simplicity and ease of manufacture, particularly whenhaving in mind the fact that the spring rod stock is readily availablefrom which the tapered springs may be fabricated. The springconstruction of the present invention also facilitates the fabricationof springs of high strength, especially as compared with compressionsprings.

lclaim:

1. Valve equipment comprising rotative valve operating mechanism, powermeans for driving the rotative operating mechanism including a motor andgearing interconnecting the motor and the operating mechanism, thegearing including a gear member serving as a reaction point fortransmission of torque through the gearing and mounted with freedom forlimited movement under the influence of such torque transmission, andyielding means for restraining said member as against said movementincluding a spring comprising a tapered rod fixedly mounted at one endand having its other end in engagement with said member.

2. Valve equipment as defined in claim 1 and further including a limitswitch for the motor operable by the springrestrained movement of saidgear member.

3. Valve equipment comprising rotative valve operating mechanism,reversibly operable power means for driving the rotative operatingmechanism including a motor and gearing interconnecting the motor andthe operating mechanism, the gearing including a member serving as areaction point for transmission of torque through the gearing in eithersense of rotation and mounted with freedom for limited movement ineither direction from a mid position under the influence of such torquetransmission, and yielding means acting to center said member in saidmid position as against movement in either direction including a springcomprising a substantially straight tapered rod fixedly mounted at itslarge end and having its small end in engagement with said member.

